@parcel/packager-js: External modules are not supported when building for browser

> 1 | import React from "react";
> | ^
> 2 | import ReactDOM from "react-dom/client";
> 3 | import { createBrowserRouter, RouterProvider, Outlet } from "react-router-dom";

this is error I found each time I run npm run build command to build app for development
due to this error i cant push my code on vercel ,same issue is there also
how can I solve this

used all the method is found on internet
used CHAT GPT also to solve this problem

1. npx parcel clean
2. npm install
3. npm install -g parcel-bundler
4. npm install parcel

tried all the methods still not working